| Item No | Recommendation | |
|---|---|---|
| Title and abstract | 1 | (a) Indicate the study's design with a commonly used term in the title or the abstract Page 2 – Lines 40–66 |
| (b) Provide in the abstract an informative and balanced summary of what was done and what was found Page 2 – Lines 40–66 | ||
| Introduction | ||
| Background/rationale | 2 | Explain the scientific background and rationale for the investigation being reported Pages 4 and 5 Lines 112–161 |
| Objectives | 3 | State specific objectives, including any prespecified hypotheses Pages 4 and 5 Lines 134–161 |
| Methods | ||
| Study design | 4 | Present key elements of study design early in the paper Page 5, 169–186 |
| Setting | 5 | Describe the setting, locations, and relevant dates, including periods of recruitment, exposure, follow-up, and data collection Page 5, 169–186 |
| Participants | 6 | (a) Give the eligibility criteria, and the sources and methods of case ascertainment and control selection. Give the rationale for the choice of cases and controls Page 5, 169–186 |
| (b) For matched studies, give matching criteria and the number of controls per case Page 5, 169–186 | ||
| Variables | 7 | Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers. Give diagnostic criteria, if applicable Supplementary data Table S2 |
| Data sources/ measurement | 8* | For each variable of interest, give sources of data and details of methods of assessment (measurement). Describe comparability of assessment methods if there is more than one group Page 5, 169–186, (cases and controls) Supplementary data Table S2 (cases) |
| Bias | 9 | Describe any efforts to address potential sources of bias Not applicable |
| Study size | 10 | Explain how the study size was arrived at Page 5, 169–186, |
| Quantitative variables | 11 | Explain how quantitative variables were handled in the analyses. If applicable, describe which groupings were chosen and why Page 7, 235–242, |
| Statistical methods | 12 | (a) Describe all statistical methods, including those used to control for confounding Page 7, 235–242, |
| (b) Describe any methods used to examine subgroups and interactions Page 7, 224–233, | ||
| (c) Explain how missing data were addressed Not applicable | ||
| (d) If applicable, explain how matching of cases and controls was addressed | ||
| (e) Describe any sensitivity analyses | ||
| Results | ||
| Participants | 13* | (a) Report numbers of individuals at each stage of study—eg numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed Page 5, 169–186, Page 9, 10, 256–289 |
| (b) Give reasons for non-participation at each stage Not applicable | ||
| (c) Consider use of a flow diagram | ||
| Descriptive data | 14* | (a) Give characteristics of study participants (eg demographic, clinical, social) and information on exposures and potential confounders Page 5, 169–186, (controls and cases) and Supplementary Table S2, (Cases) |
| (b) Indicate number of participants with missing data for each variable of interest Supplementary Table S2 | ||
| Outcome data | 15* | Report numbers in each exposure category, or summary measures of exposure Page 9, 10, 256–289 (controls) and Supplementary Table S2 (cases) |
| Main results | 16 | (a) Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (eg, 95% confidence interval). Make clear which confounders were adjusted for and why they were included Page 9, 10, 256–289 and Supplementary Table S2 |
| (b) Report category boundaries when continuous variables were categorized Supplementary Table S2 | ||
| (c) If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period Page 9, 10 256–289 | ||
| Other analyses | 17 | Report other analyses done—eg analyses of subgroups and interactions, and sensitivity analyses Page 8–10, 248–371 |
| Discussion | ||
| Key results | 18 | Summarise key results with reference to study objectives Page 10- 371–379 |
| Limitations | 19 | Discuss limitations of the study, taking into account sources of potential bias or imprecision. Discuss both direction and magnitude of any potential bias Page 13, 450–469 |
| Interpretation | 20 | Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies, and other relevant evidence Pages 11–13, 373–469 |
| Generalisability | 21 | Discuss the generalisability (external validity) of the study results Pages 11–13, 373–469 |
| Other information | ||
| Funding | 22 | Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based Page 7, 244–246 |
*Give information separately for cases and controls.
Note: An Explanation and Elaboration article discusses each checklist item and gives methodological background and published examples of transparent reporting. The STROBE checklist is best used in conjunction with this article (freely available on the Web sites of PLoS Medicine at http://www.plosmedicine.org/, Annals of Internal Medicine at http://www.annals.org/, and Epidemiology at http://www.epidem.com/). Information on the STROBE Initiative is available at http://www.strobe-statement.org.